The prior art includes turf aerators which are mobile over the ground and form perforations in the ground when the machine advances on the ground. In various constructions of aerators, the aerator tines or perforators themselves operate in a variety of actions. That is, some are arranged to move into the ground at an advancing angle and then retract at a complimentary angle, like a person using a walking stick, and others are arranged to penetrate the ground in a closely vertical action to thereby provide only a minimum of upset or displacement of the turf adjacent the desired vertical hole. In all instances, the tines are positioned forwardly and then penetrate the ground and the machine is moved over the point of penetration and then the tine is retracted from the ground. Arrangements are made to move the retracted tine to a forward position where it can again penetrate the ground and repeat the perforating action.
Prior art mechanisms for actuating the tine include crankshaft systems for moving the tine up and down relative to the ground level, and also include springs for returning the tines to the forward position prior to penetrating the ground.
With regard to the present invention, even more significant is prior art which utilizes a walking-type principle where a pair of tines is arranged side-by-side such that when one tine is advanced and moved into the ground, the other tine is in a retracted position and ready to be advanced when the penetrating tine eventually moves rearwardly, all in a walking-type action created between the two tines which are going up and down and relatively forward and back. Examples of the walking-type of prior art aerator are shown in U.S. Pat. Nos. 2,638,831 and 4,750,565. Additionally, U.S. Pat. No. 2,638,831 shows a spring arrangement for returning the walking tine to a forward position, and also U.S. Pat. Nos. 3,986,562 and 4,658,909 show spring arrangements for returning the tine to the forward position ready to penetrate the ground.
In the prior art spring return systems, and in U.S. Pat. No. 4,750,565, there is no provision or arrangement for placing the walking tines in a centered or neutral position when they are free of the turf so that they can be placed in the optimum starting point of neutral positioning mentioned. Instead, the prior art tines are subject to the full force of the return spring, as mentioned in those patents, or they are subject to the linkage arrangement which inherently positions one tine only relative to the other tine and that may be in a forward and a rearward position, rather than in a centered or neutral position mentioned, as in U.S. Pat. No. 4,819,734.
Accordingly, the present invention improves upon the prior art by providing a turf aerator mechanism wherein the tines can be positioned in a centered or neutral position when they are free of the ground, and thereby provide for an optimum starting point for the aerating process.
Another object and advantage of this invention is to provide a turf aerator wherein the tines do utilize the walking principle so that they are in phase of forward and rearward action when one of the tines is penetrating the ground, and to accomplish this, the tines are mechanically interconnected to assure this action. Furthermore, the present invention provides for the neutral or center positioning of the tines when the tines are free of the ground, and such centering action is automatic and by virtue of a reliable and efficient arrangement which in actuality includes a single spring effective on both of the walking tines.
Still additionally, the present invention provides for the turf aerator with the walking principle for the tine and wherein the tines are guided in their vertical action by slots flanking the sides of each tine to thereby eliminate any requirement for mechanism which would guide the tines laterally of the fore and aft direction of machine movement such as is required in U.S. Pat. No. 4,750,565.
Somewhat more generally, the present invention provides a turf aerator which has a minimum of operating noise and wear, and also only a minimum of maintenance would be required to maintain the turf aerators of this invention, all because the apparatus for controlling the tines is simplified but yet most effective and provides for novel action, such as the centering and neutralizing mentioned above.
Other objects and advantages will become apparent upon reading the following description in light of the accompanying drawings.